Dhaka , Bangladesh -LRB- CNN -RRB- At least six people have died and more than 60 were injured after the roof of a partially built cement factory collapsed Thursday in southwestern Bangladesh , police and fire officials told CNN .

Many of those injured were in critical condition , said Mohammed Bakir Hossain , the top government physician of Bagerhat district .

Mohammad Niazmur Rahman , the fire and civil defense official coordinating the search and rescue effort , said early Thursday evening that two people had been pulled alive from the rubble and as many as 30 others are believed to be still trapped .

Deputy inspector general of police of Khulna range SM Monir Uz Zaman said the number of those still trapped was unclear `` as we 're not sure how many people were working inside . ''

The collapse took place around 1 p.m. -LRB- 3 a.m. ET -RRB- in Mongla , a port city in the Asian nation 's Bagerhat District . The factory is owned by Sena Kalyan Sangstha , a welfare organization for former Bangladeshi troops and their beneficiaries , according to Rahman and other local officials .

Video from Boishakhi TV showed medical workers tending to the injured as they were wheeled into a local medical facility caked in dust .

Deadly incidents at factories and other buildings , sadly , are nothing new in Bangladesh .

The worst happened on April 24 , 2013 , when a nine-story building that housed five garment factories collapsed . Rescuers managed to save the lives of more than 2,400 people , but more than 1,100 died in the horrific accident .

And a November 2012 apparel factory fire on Dhaka 's outskirts killed at least 117 people , some of whom jumped from the building to escape the flames . Most of the dead were women , almost half of them burned so badly that DNA tests were needed to identify them .

That blaze led to the convictions of 13 people for gross negligence of safety measures and spurred widespread criticism about the state of workers ' rights in Bangladesh .

The government responded by revamping laws so that workers no longer need approval from employers to form trade unions , and every factory that sells within the country also has to pledge 5 % of their profits toward a workers ' welfare fund . The government also boosted minimum wages from $ 38 to around $ 68 per month .

Yet this has n't stopped more deadly incidents , including the January deaths of at least 13 people when a fire broke out inside a Dhaka factory .

Farid Ahmed reported from Dhaka and Harmeet Shah Singh from New Delhi . Greg Botelho wrote this story from Atlanta . CNN 's Sugam Pokharel and Kunal Sehgal contributed to this report .

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More than 60 are injured , many critically , official says

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The cement factory was owned by a Bangladeshi army welfare organization

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In recent years , Bangladesh has had other deadly incidents at factories